Hausner was found guilty after a gun crazed slay spree – terrorizing the Phoenix, Arizona area for 14 months in 2005-06.

Hausner, a former janitor at an airport was sentenced to six death sentences and hundreds of years in prison for shooting dead six people and attacking 19 others. He was one of the key suspects in the "Serial Shooter" case.

Last month, Hausner was found comatose and unresponsive in his cell at the Eyman state prison complex.

According to Arizona Department of Corrections officials, he was pronounced dead an hour later at a local hospital.

The cause of death was ‘amitriptyline intoxication’ which is an antidepressant medications often sold under the brand name Elavil.

Toxicology reports following his autopsy said Hausner had 50 times the recommended dosage in his system at time of death.

It is unclear how the killer was able to obtain the drugs while on death row,